Electronic switching circuit



NOV- 27, 1951 R. c. wrrTl-:NBERG 2,576,552

ELECTRONIC SWITCHING CIRCUIT Filed Aug. 1l, 1950 Patented Nov. 27, 1951 UNITED STATES PATENT OFFICE;

ELECTRONIC SWITCHING CIRCUIT Roland C. Wittenberg, Mineola, N. Y., assigvnorl to The Sperry Corporation, a corporation of Delaware Appiieetion August 11, 195o, serial No. 178.931

v5 Claims. (Cl. Z50-27) 'This invention relates to electronic vswitches l and more particularly to a switching circuit suited to control the operation of a two-speed -servo mechanism.

An object of the invention is toprovide an electronic switching circuit of the above type in whichthe control signal to the servo mechanism is blocked whenever the signal falls below apre- Adetermined value. y Y

vAnother object is to provide a cut-in system of the above type in which a low noise level is maintained prior to cut-in.

The invention is particularlyvv applicable to a two-speed servo mechanism wherein the servo is normally under the control of a ne control signal but is brought under the control of'a coarse control signal whenever the coarse control signal exceeds a predetermined value. Below this value the coarse control signal `is blocked by the electronic switching circuit and does 'not appear in vtheoutput circuit. Above that value the coarse lcontrol signal is superimposed on" the ne control signal in the usual manner. t

The novel features which are" characteristic of l'this invention wiube better understood by re-` ferring to the following description,'taken in connection with the accompanying vdrawings in which certain specific `embodiments have been set forth for the purpose of illustration.

' In thefdravvings:V Fig.r 1 is'a schematic diagram of an electroni switching circuit embodying the present invention;and l Fig. 2 is a schematic diagram of a similar cirl :uit'illustrating a further embodiment of the vinvention. y 7 Referring to Fig. 1, the coarse `'E1n is' applied across input terminals III and II, the latter being grounded. The terminal I is connected byline I2 through condenser I3 to a vgas`tube I4, thencebyline I5 to the cathodeli .of a rectifier I1.

control signal n The anode of the rectifier I1 is connected by a lead I9 'to the grid'2Il of atriode2 I having a cathode 22 which is connected to suitable source of negative potential 23. A resistor is connected betweenthe junction of the condenser I3 and gastube I4 andthe source 23. vA resistor 26 and condenser 2'I are, connected in parallel between the anodeoffrectier I'I and the D. C. source 23. i

The anode of the triode .2| is connected by fa llead 30 to the suppressor grid 3'I of -a pentode 32 and is grounded through a high resistor 33. The plate 34 and screen grid 35 of the pentode 32 are connected through resistors 3B and 31, re-

32 is grounded by a lead 42. 43 of said pentode is connected by a lead 44 to spectively, to a source of. positive potential 38. The anode 34 of the pentode 32 is connected to an output terminal 40, the other output terminal 4I being grounded. The cathode of the pentode The control grid minus potential which is applied at terminal 2,3.

This results in vcutting off the pentode output voltage is zero.

When. the input voltage is larger than the break down vo-ltage of the gas tube I4 this tube becomes conducting, the signal is rectied by the rectier I'I and a'negative bias is applied 'to 32 andthge ythe grid "of -the triode` 2|, thereby blocking lthe .trio'de 12| and allowing the suppressor grid of the pentode32 to return to ground potential. The pentodeisthen vallowed to pass current and the input signal which is supplied to the control grid 43 ofthepentode by `theline 44 is amplified-by the 'pentode and appears' as the output signal at the output terminals andj4I.

,The time constant of the condenser ZI'anduregsistor 26 should be suicient as compared to the period o f the input/,signal so that the grid voltage Toi the triode 2| after cut-in is never above the tube cut-olijf voltageand it must be small enough .sp that the switching'time has a negligible effect on the servo mechanism response characteristics.

Condenser I3 isused as a D. C. blocking condenser and the resistor 25 provides a discharge path therefor. 'I K 1 `.Itv will be noted that in the above system the output voltage is` equal to the input voltage ztimes the amplification factor of the pentode 32. whenever the input-voltage exceeds a value sunicient .tounblock the pentode. When the input voltage is below this value the pentode remainsblocked n when the output signal is zero level.

Fig. 2 represents a typical circuit to be used for servo 'control purposes. In thisI figure 50 represents the secondary vof the' transformer carrying the input signaltand connected to input terminals II and 52. The terminal 52 is grounded and the terminal 5I is connected through resistor 53 to 

